Recovery of hydrocarbons from fuel gases



April 7, 1942. P. E.KUHL 2,278,999.

RBGOVERY'OF HYDROCARBONS FROM FUEL GASES Filed March 17, 1959 v- GAS TR ESH IL INLET .STfi/PP/NG STILL C004 15 FFFE are: 0/1. r0

sauezaronfrom the bottom of cooler I Patented Apr. 7, 1942 OFFICE I RECOVERY OF HYDROCARBONS FROM I FUEL GASES Paul E. Kuhl, Madison, N. J., assignor to Standard Oil Development Company, a corporationof Delaware Application March 17, 1939, Serial No. 262,376 1 Claim. (Cl. 183-114.6)

The present invention relates to the recovery of products produced in the manufacture of various industrial gases. The invention is especially concerned with improved apparatus and methods for the recovery of gasoline produced in the manufacture of carbureted water or producer gas. In accordance with the present process, products produced in the carburetion of industrial gases are efiiciently and economically recovered by a particular sequence of stages comprising a two-stage direct cooling process.

It is well known in the art to produce industrial gases by various methods and to enrich these gases by carbureting with petroleum oils. These processes utilize a generator in which the carbonaceous product, usually coal, is raised to an incandescent temperature. Steam is then passed through the incandescent bed, resulting in the formation of hydrogen and carbon monoxide. Petroleum oil is injected into the system under conditions which result in the vaporization and cracking of the oil. The oil may be injected in the generator or may be admitted in a carburetor which is usually a fire brick lined vessel filled'with checkered brick and provided with an oil spray. The gases removed from the generator and carburetor contain water gas, a certain amount of air gas, oil gas, gasoline, cycle oil, tar and coke dust. The removal of these products from the water gas has involved considerable My invention is pardifliculties and expense. ticularly directed to the economical purification ing cold cycle oil which is supplied by means of line 9 in suficient quantity to cooler 8 to reduce the temperature of the gases to the point de sired for subsequent absorption. The gases are removed overhead from cooler 8 and may be compressed in compressor I0. The compressed gases then pass into the bottom of absorber II by means of line I2. In absorber II the gases flow upwardly and countercurrently contact lean oil which is introduced into absorber II by means of line I 3. The stripped dry gas is removed overhead from absorber I I by means of line I4,

- by means of line I3. Fresh oil for the carburetof industrial gases secured by these'operations f and the efficient recovery of the by-products.

The process of my invention may be readily understood by reference to the attached drawing illustrating one modification of the same. Gases from a water gas generating'system are led into the bottom of an initial cooler I' by means of feed line 2. These gases flow upwardly through cooler I'and contact downflowing recycle oil introduced into cooler I by means of feed line introduced by means of line by means of line 5 and cooled indirectly by water in exchanger 6 and then returned to the top of gas cooler I by,

means of line 3. Accumulation of oil in the by means of line 3 and also contact fresh oil which is 4. Oil is removed system is avoided by returning to the generator by means of line 1 the amount of oil condensed in cooler I, as well as the amount of oil introduced by means of line 4. The gases are removed overhead from cooler I and introduced into the bottom of a second cooler 8. The gases flow upwardly in coolerB and contact downfiowfractions not introduced into ing system may be'introduced into absorber II by means of line 22. The fresh feed oil contain- 'ing the absorbed products is then led into stripping still -l6 by means of line I! and the absorbed" products removed as described above. The stripped fresh feed oil is removed from stripping ,still I6 by means of line 2'I Qand then introduced x into the carbureting system by means of line 23.

Undercertaini operating conditions it may be desirable to. introduce at least a portion of the .lean oil into coolerI by means of lines 21 and I. on from the bottom of the second cooler is withdrawn by means of line'24, cooled indirectly with F water in cooler 25 and then returned to the top of cooler 8. Oil equivalent tothe' amount of oil condensed in cooler 8 is withdrawn and introducedinto cooler I as fresh feed oil to cooler I by means of line'4. If additional fresh -feed oil'is required in cooler I it may be introduced 21 or by means of line 28. If desirable, oil or water may be introduced or withdrawn from cooler B by) means of line 29. Ho ever, any accumulation of oil in cooler 8 due to'condensation of cycle oil and gasolineof line 4 is preferably withdrawn by means of line 26 and combined with the rich oil from the absorber to the stripping still by means of line 26. It may be desirable under certain conditions to introduce a portion of the feed, oil into the carburetor by means of line 21' through absorber II and stripping still I6 and introduce the remaining oil by means of line 30. p

The process of the present invention may vary and led into dis- 7 cooler I bymeans widely and the conditions adjusted to secure optimum results with respect to the particular cycle oilbeing used and the amount and type of impurities from the carburetor system. It is essential that a two-stage direct cooling system be employed and that the coke deposit and the tarry matter be removed in the initial cooler. In order to secure this the'gases are cooled in an initial stage from about 800 For higher to a temperature in the range from 400" to 450 F. In order to secure optimum results it is desirable that two oil sprays be included in cooler I, the

lower of these sprays being oil-picked up from the bottom of cooler I and circulated through an indirect, cooling device to a point higher in the tower. This spray will knock back most of the tar and coke dust. The upper oil spray should be clean 011, preferably from the bottom of the second cooler, which will serve to remove substantially all of the remaining coke, dust and tar so that a clean gas will be introduced into the secondary cooler. I

The pressures employed in the coolers are preferably atmospheric, although other pressures may be employed. The quantity of oil employed in scrubbing the gases is of a suflicient quantity so that exit gases leaving the initial cooler will have a temperature of approximately 375 to 425 F. In general, it is preferred to utilize about 15% of recycle oil withdrawn from the bottom of the primary cooler and about of relatively clean oil withdrawn from the bottom of the secondary cooler. Un-

der certain conditions, however, it may be desirable to use approximately 50% recycle oil and 50% relatively clean oil. The exit gases from the primary cooler are then further cooled to a temperature in the range from about 75 to 125 F. in a secondary direct oil cooler. The quantity of oil used in thesecondary cooler will likewise be sufficient to reduce the temperature of the gases to this temperature. The exit gases from the secondary cooler are preferably compressed to about 50 to 150 lbs. and introduced into the absorber. The temperature and pressure conditions maintained in-the absorberfwill depend upon the particular absorber oil being used, as

well as upon the composition of the gases. In general, it is preferred to absorb the gases at a temperature in the range from 50 to-120 F. at

a pressure of from 50 to 150 lbs. per square inch..

The gas from the generator contains a con- Example Gasoline, volume: per cent 30-35 Total uncracked gas oil, weight do 6-20 Oil to water gas do 2- 6 Oil g do 50-60 Total gas cubic feet per hour about 400 The gasoline had an inspection as follows: Gravity per cent '44- 88 Initial boiling point 80- 90 10% oil at. degrees Fahrenheit 120-135 20% ofl at do 160-210 30% off at :10 190-240 40% off a do 240-310 ofl. a do 300-340 off a do 315-360 of! a do 340-375 off at do 360-385 off at do 380-400 Final boiling point do 400-420 The inspection of the finished gaswas as :01-

When this gas was treated in accordance with 1 the processor the present invention, the coke,-

dust and tarry matter were removed in the initial cooler and the heavy coke and tar removed from the bottom of said cooler. Clean oil was removed from the bottom of the secondary cooler and the gasoline removed from the overhead eases of the secondary cooler by absorption in ,the absorber. Dry gas was removed from the overhead from the absorber.

The present invention is not to be limited by any theory or mode of operation, but only by siderable amount of coke, dust and tarry matter I which is removed in cooler I generally by the lower spray The upper spray comprising clean oil from the secondary cooler removes the remainder of the coke, dust and tar so'that a cleangas is introduced into the secondary cooler.

" Heavy'tar and coke .are removed from the primary tower from below the level at which the circulation oil. is withdrawn.

The present ir-iv'ention secures efiicient heat transfer and puriilcation of the generator gases. In the primary cooler a large part of..the oil from the bottom of the secondary cooler will be revaporized' and returned to the secondary cooler, thus utilizing the latent ,heat of the cooling medium. Theinvention is particularly applicable in the treatment of. lean gases. H v

In order to further illustrate the invention, the following example is given which should'not be construed as limiting the same in any. manner whatsoever.

-the following claims in which it is desired to claim all novelty in so far as the prior art permits.

I claim:

Process for the purification of carbureted water and producer gas and for the recovery therefrom of hydrocarbon constituents boiling in the gasoline boiling range, comprising passing said carbureted gasthrough an initial countercurrent direct oil cooler containing .two oil sprays, one disposed above the other, under conditions to remove therefrom entrained'solid particles and hydrocarbon fractions boiling above the gasoline boiling range, passing the cooled gases through a secondary countercurrent directv oil cooler under conditions to condense a substantial amourt of the hydrocarbon fractions boiling in the gasoline boiling range, removing cooled gases from said-secondary cooler and subjecting the same in an absorption. stage to countercurrent contact with an absorption oil under conditions to'prdduce a gas substantially free of hydrocarbon constituents boiling in the gasoline boiling range,

removing said absorption oil and recovering hydrocarbon constituents therefrom in a distillation stage, said lower oil spray of said initial cooler comprising recycle oil withdrawn from the lower portion of said initial cooler and said upper oil spray of said initial cooler comprising clean oil containing gasoline constituents withdrawn from the bottom portion of said secondary cooler so that cooling of said initial cooler is obtained by evaporation of atleast part ofthe gasoline'con- 5 stituents.

PAUL E. KUHL. 

